Objective: The aim was to conduct a semi-objective analysis of phonetic alterations in patients during the first 24 h after being fitted with F22 aligners. Our secondary objective was to analyse the patients' perception of any speech impediments caused by the aligners, and the impact of such alterations on their daily lives. Methods: Thirty patients were given the Fanzago articulation test at three different time points defined as T0 (before aligner fitting), T1 (immediately after aligner fitting) and T2 (24 h after aligner fitting), and results were evaluated independently by three speech therapists. Patients were also asked to fill in a questionnaire consisting of six items on their perception of any phonetic alterations provoked by the aligners, and the influence of this on their daily lives. Results: The results of the semi-objective analysis based on the Fanzago articulation test revealed the alteration of only three phonemes of the 28 assessed, specifically "s", "ts" and "ʃ". Furthermore, these alterations were only found in four out of 30 patients at T1, and three out of 30 patients at T2. The questionnaire revealed that 28 out of 30 patients perceived some speech anomalies, but that this had no significant impact on their daily lives. Conclusions: These findings show that F22-aligner therapy has no significant impact on patients' phonetic articulation; the alterations detected were slight and involved only three phonemes, "s", "ts" and "ʃ". Keywords: F22 aligner, orthodontic aligners, phonetic alterations